A fluorine-containing resin and a fluorine-containing rubber have excellent properties such as heat resistance, oil resistance, solvent resistance, chemical resistance and the like as compared with resins and rubbers for general uses, and are used widely as industrial materials in the field where these properties are required. While making the best use of these excellent properties, further three properties such as semiconductivity, non-tackifying property and high dielectric property are demanded depending on applications.
For example, in the fields of image forming members for electrophotographic copying machines, facsimile machines and printers, a material having well balanced properties such as semi-conductivity, non-tackifying property and high dielectric property is required for charging members, transferring members and feeding members.
Namely a high dielectric property is required in order to conduct charging and image-transferring efficiently and feed papers securely. Also it is required that the material is semi-conductive in order to remove an induced charge immediately and prevent disturbance of an image due to occurrence of discharging at peeling off. Further in order to prevent contamination of each of the above-mentioned members by a toner and paper dust, it is required not to lower the excellent non-tackifying property which the fluorine-containing resin and fluorine-containing rubber possess inherently. Thus the above-mentioned members satisfying all these three properties are demanded.
For example, JP-A-7-295391 discloses an image-transferring belt of a three-layer structure comprising an inner layer of a medium-resistant rubber material, a dielectric layer as an intermediate layer and an electrically resistive layer as a surface layer containing dispersed carbon particles in order to provide an image-transferring belt which assures good feeding property and separability of papers and can give a good image stably. Also in case of a full-color copying machine and the like, it is necessary to transfer a toner image formed on a surface of an electrophotographic sensitive member onto an image-transferring material by multi-color transfer of 3 or 4 colors, and therefore a step-up for changing transfer conditions is carried out with increase in a number of feedings and thus higher voltages are applied in order. Therefore the image-transferring member having a large dielectric constant is desirable from the point that a large amount of electric charges can be maintained at low voltage. JP-A-7-281535 discloses a dielectric carrier article for image-transferring material which is obtained from a composition comprising a vinylidene fluoride resin and a methyl methacrylate resin in order to provide a dielectric article which assures a small change of a volumetric resistivity against change in humidity and temperature and has a high dielectric constant. Also JP-A-7-110582 discloses an electrostatically adsorbable and removable sheet which is used as an electrophotographic transfer sheet, paper adsorbing sheet of printers and the like and comprises a non-stretched thin dielectric article obtained by melt-extruding a vinylidene fluoride resin and barium titanate powder in order to improve electrostatically adsorbing and removing characteristics and a tearing strength.
However there is a problem that any of the members described in those patent publications cannot satisfy the above-mentioned three properties.
Further JP-A-7-149448 discloses an electrically conductive and non-tackifying roller in which an electrically resistive layer comprising a composition containing carbon fluoride particles with a molar ratio F/C of fluorine atom to carbon atom of more than 0.5 and less than 1.0 is provided on an electrically conductive supporting body. Though proper electric conductivity and non-tackifying property are obtained, it is desired to further improve a dielectric property. Also according to the process described in that publication, carbon fluoride particles which are fluorinated only in their surface region or up to the inside thereof uniformly and thus have a medium degree of fluorination can be obtained. There is a problem, however, that even by controlling reaction conditions by any means, it is difficult to stably obtain a mixture of highly fluorinated carbon fluoride particles and slightly fluorinated carbon fluoride particles.
Also in order to impart the above-mentioned semiconductivity to a resin composition and rubber composition, an agent for imparting electric conductivity, for example, carbon black, carbon fiber, metal powder, ionic surfactant or the like has been used. In order to impart the above-mentioned non-tackifying property, an agent for imparting non-tackifying property, for example, a fluorine-containing oil, a fluorine-containing resin such as tetrafluoroethylenehexafluoropropylene copolymer, silicone oil or the like has been used. Further in order to impart the above-mentioned high dielectric property, an agent for imparting a dielectric property, for example, lead zirconate titanate lanthanate, lead zirconate titanate, barium titanate or the like has been used.
However in case where the three properties are needed at the same time, there are problems that not only a satisfactory performance cannot be obtained only by simply mixing the above-mentioned three agents but also since the above-mentioned agent for imparting conductivity and agent for imparting high dielectric property are substances having a high surface energy, even if the agent for imparting non-tackifying property is used, lowering of the non-tackifying property cannot be avoided and even if a fluorine-containing resin and fluorine-containing rubber are used as the above-mentioned resin and rubber, only a composition having non-tackifying property lower than inherent non-tackifying property of the resin and rubber can be obtained.
An object of the present invention is to provide an image forming member for electrophotographic copying machines, facsimile machines and printers. Because the member has semi-conductivity, non-tackifying property and high dielectric property, the member has a high charging efficiency and image-transferring efficiency, is excellent in feeding property and separability of papers, is free from jamming of papers and can give a good image stably. The other objects are to provide a paint used for the member; a carbon fluoride composition used for the paint; a composite material comprising fine particles of carbon fluoride; and a process for preparing the composite material.